[x86] Teach the new vector shuffle lowering to widen floating point

elements as well as integer elements in order to form simpler shuffle
patterns.

This is the primary reason why we were failing to match some of the
2-and-2 floating point shuffles such as PR21140. Even after fixing this
we need to support some extra patterns in the backend in order to match
the resulting X86ISD::UNPCKL nodes into the correct instructions. This
commit should fix PR21140 and includes more comprehensive testing of
insertion patterns in v4 shuffles.

Not all of the added tests are beautiful. For example, we don't have
clever instructions to insert-via-load in the integer domain. There are
also some places where we aren't sufficiently cunning with our use of
movq and movd, but that's future work.

llvm-svn: 218911

1 files changed, 9 insertions, 8 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index cb27a43558f..9089d138ddc 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -10252,16 +10252,17 @@ static SDValue lowerVectorShuffle(SDValue Op, const X86Subtarget *Subtarget,
         return DAG.getVectorShuffle(VT, dl, V1, V2, NewMask);
       }
 
-  // For integer vector shuffles, try to collapse them into a shuffle of fewer
-  // lanes but wider integers. We cap this to not form integers larger than i64
-  // but it might be interesting to form i128 integers to handle flipping the
-  // low and high halves of AVX 256-bit vectors.
+  // Try to collapse shuffles into using a vector type with fewer elements but
+  // wider element types. We cap this to not form integers or floating point
+  // elements wider than 64 bits, but it might be interesting to form i128
+  // integers to handle flipping the low and high halves of AVX 256-bit vectors.
   SmallVector<int, 16> WidenedMask;
-  if (VT.isInteger() && VT.getScalarSizeInBits() < 64 &&
+  if (VT.getScalarSizeInBits() < 64 &&
       canWidenShuffleElements(Mask, WidenedMask)) {
-    MVT NewVT =
-        MVT::getVectorVT(MVT::getIntegerVT(VT.getScalarSizeInBits() * 2),
-                         VT.getVectorNumElements() / 2);
+    MVT NewEltVT = VT.isFloatingPoint()
+                       ? MVT::getFloatingPointVT(VT.getScalarSizeInBits() * 2)
+                       : MVT::getIntegerVT(VT.getScalarSizeInBits() * 2);
+    MVT NewVT = MVT::getVectorVT(NewEltVT, VT.getVectorNumElements() / 2);
     V1 = DAG.getNode(ISD::BITCAST, dl, NewVT, V1);
     V2 = DAG.getNode(ISD::BITCAST, dl, NewVT, V2);
     return DAG.getNode(ISD::BITCAST, dl, VT,